This invention relates generally to an adapter cushion for use in a press or the like with a die assembly having a plurality of projecting pins.
Adapter cushions have previously been utilized in sheet metal forming presses to yieldably load various elements of a die. These known adapter cushions have previously included one or more plates which have cooperated with a cylinder block or spacer bar and with piston and cylinder units. The pistons are forced axially outward relative to the cylinders by fluid pressure in the cylinders to provide a yieldable loading for the push-pins of a die assembly. One of these known adapter cushions is disclosed in U.S. Pat. No. 3,457,765. Generally similar adapter cushions are commercially available.
Fluid leakage is a problem which can be encountered with a known adapter cushion which is formed by interconnecting one or more plates with a cylinder assembly or casting. If a plate is not accurately machined to have a flat smooth surface and if it is not engaged by a cooperating flat smooth surface, high pressure gas can leak through joints formed with the plate. In addition, even if the plate is originally formed with a very flat smooth surface, the plate can become nicked or slightly warped during extended usage in such a manner as to result in the leakage of gas. Of course, it is relatively expensive to form a large plate with a perfectly flat smooth surface which will provide a joint with a mating surface which will not leak when exposed to gas at a pressure of 1500 psi.
Many adapter cushions are constructed to be utilized with die assemblies having different pin arrangements. If one of these pin arrangements is such that a die pin is not associated with a particular cylinder, the flow of gas from the inactive cylinder can be blocked by either a piston and its associated seal or by plugging an opening through which gas flows to the cylinder. With certain known adapter cushions, the die pin enters the cylinder through one end and high pressure fluid enters the cylinder through the opposite end. The plugging of the fluid passage at one end of a cylinder requires a substantial amount of time since the passage is relatively inaccessible.
During operation of known adapter cushions, there is a substantial amount of noise. This is due to engagement of a die pin with the end face of a piston and engagement of the piston with the end of a cylinder. Although the noise may be acceptable in certain environments, in other environments the noise is objectionable.
Efforts have previously been made to retrofit adapter cushions to existing presses. Although adapter cushions have been retrofitted into many presses and have enhanced their operating characteristics, difficulties have been encountered in retrofitting adapter cushions into certain presses. In order to minimize these difficulties, the stroke and overall height of an adapter cushion should be minimized. Of course, the overall height of an adapter cushion tends to be increased by the presence of relatively thick end plates and/or relatively long pistons.